1. Field of the Invention
This invention relates to an optical data recording and reproducing method. More specifically, this invention relates to an optical disk recording and reproducing method which makes possible to record data encoded by different encoding circuit at different data compression rate and to reproduce the data.
2. Description of the Prior Art
Initialized by the vast increase in information that needs to be processed, optical data storage system have become very important system particularly because of their high storage density per area. Most of the recent optical information storage systems rotating single optical disk are used on which the information is digitally stored in concentric circular tracks in an ordered, predefined manner to allow chronological fast reading and fast random access to desired pits of data.
In order to accomplish even more storage capacity of optical disk systems for enormous information processing, such as video or picture communication like so called video-on-demand service, multiple disk systems have been proposed. An optical disk system equipped with two or more data layers may in theory be accessed as different disks by changing the focal point with moving lens. Example of this type of state-of-the-art include U.S. Pat. No. 5,202,875 issued Apr. 13, 1993 to Rosen et al.; Japanese Published Application, 63-276732 published Nov. 15, 1988 by Watanabe, et al.
Such a multiple disk recording and reading system is applied to varied optical disk information storage systems. For example, a digital video disk (DVD) system for home entertaining is one of the typical application. The mentioned advantage of vast storage capacity may contribute especially for video signal transmission. In order to record the video data efficiently onto the optical disk, a video data compression technique is one of the key technologies. A standardized video data compression rate has been proposed, which is called MPEG (Moving Picture Experts Group). However, for the home entertaining purposes, a more flexible function is required. The ability to record data at different data compression rates and to reproduce the recorded data, must be provided.